1. Technical Field
The present invention relates in general to improvements in computer based manufacturing systems and in particular to improvements in determining optimal routes for moving materials between workstations in a computer based manufacturing system. Still more particularly, the present invention relates to a method and system for automatically determining an optimal route among many available routes for transporting materials between workstations within a computer based manufacturing system.
2. Description of the Related Art
Computer based manufacturing systems are well known in the art. The process of designing, developing and manufacturing a new product, or making major changes to existing products, presents many challenges to product managers and manufacturing managers. It is important to maintain product quality while bringing a product to market for the least cost, within a set schedule. In today's highly competitive industries, product managers and manufacturing managers require information to address many problems which arise because of the complexity of new products and the complexity of world-wide production and the changing nature of competition. A requirement that products be manufactured for the least possible cost is an important requirement in all industries.
Many texts have been written concerning the field of production management. For example, Joseph Orlicky wrote Material Requirement Planning, published by McGraw-Hill, which has become the industry standard reference for almost all job shop planning requirements. This concept of planning and releasing work to the manufacturing shop floor is well accepted and, even today, many vendors are selling software based upon this concept. From a dispatching point of view, this system takes into account only the general concept of a first-in, first-out (FIFO) basis of dispatching. Dr. D. T. Phillips and G. L. Hogg published a paper entitled A State-of-the-Art Survey of Dispatching Rules for Manufacturing Shop Operations, International Journal of Production Research, Volume 20, No. 1, pages 27-45, which provides varying dispatching rules which may be utilized in a planning process.
International Business Machines Corporation has developed a product called "Capacity Planning and Operation Sequencing System (CAPOSS)", described in Education Guide No. SR19-5004-0, published by International Business Machines Corporation, which provides static dispatching functions in the form of deciding the next operation to be performed for an order after completion of a prior operation.
One important feature in modern day manufacturing facilities is the need for an improved parts and materials supply system which is necessary to minimize inventory and floor space required for parts storage at the workstations. The efficiency and economy of so-called "just in time" inventory control systems is now well recognized and many systems have been implemented which attempt to impose such a delivery system. For example, U.S. Pat. No. 4,669,047 discloses an automated parts supply system which may be utilized to implement a "just-in-time" supply system.
U.S. Pat. No. 4,472,783 describes an improved flexible manufacturing system which utilizes multiple numerically controlled machine tools. In accordance with a supervisory control computer the system described therein supplies routing information to the material handling system controller which in response, controls the movement of pallets through a manufacturing production path to various machine tools. This system deals with a novel method of controlling a specific type of manufacturing line.
Similarly, U.S. Pat. No. 4,561,060 describes a system for controlling the flow of articles within a work area which includes multiple workstations and for acquiring real time information relating to the status of the work in progress.
None of the above described methods disclose a means for determining the best method, among available alternatives, for transporting materials and product between work centers, while considering various factors such as fragility, size or weight. Modern systems have become so complex that it is not uncommon for multiple modes of material movement to be available for transferring product between locations within and among manufacturing work centers and the availability of such multiple modes of transportation has substantially increased the complexity of the tasks of determining an optimal path for product to be transported within a computer based manufacturing system. Further, a manufacturing process may be distributed over a wide geographic area, requiring a much more sophisticated level of control for transport of product throughout the process. It is therefore obvious that a need exists for a method and system which may be utilized to optimize the movement of material within a manufacturing process within a dynamic, changing environment.